Applicant has found that the invention of this application works particularly well with the drilling and inspection of drilled pile shafts or boreholes wherein the reference “borehole” is being used throughout this application. However, this application is not to be limited to drilled pile shafts or boreholes wherein reference to piles and/or boreholes in this application is not to limit the scope of this application. In this respect, the invention of this application can be used in connection with any deep excavation wherein the quality, shape, radius and/or verticality need to be determined and/or measured. Yet further, the invention of this application can also be used for measuring other openings such as slurry walls or any other extended openings. Similarly, “piles” can equally refer to drilled shafts or other deep foundation elements. Thus, boreholes can equally refer to any opening in a layer, such as a ground layer and any other excavation, such as a slurry wall. Application to shallow foundations and/or openings is also useful.
Sensing apparatuses have been used in the building and construction industry for a number of years. These sensing apparatuses include a wide range of devices used for a wide range of reasons in the field. These devices include sensing devices that are used in connection with the installation and use of supporting elements such as piles that are used to support the weight of superstructures such as, but not limited to, supporting the weight of buildings and bridges. As can be appreciated, it is important to both ensure that a supporting foundation element, such as a pile, has been properly formed and installed and that structurally it is in proper condition throughout its use in the field. It must also have sufficient geotechnical bearing capacity to support the applied load without excessive settlement.
With respect to the installation of piles, it is important that these structures be properly constructed so that the pile can support the weight of a building or superstructure. Thus, over the years, systems have been designed to work in connection with the installation of a pile to ensure that the pile meets the building requirements for the structure. These include sensing devices that work in connection with the driving of a pile as is shown in Piscsalko et al., U.S. Pat. No. 6,301,551. Again, the Piscsalko patent is incorporated by reference herein as background material relating to the sensing and driving of structural piles. These devices help the workers driving these piles to determine that the pile has been properly driven within the soil without over stressing the pile during the driving process, and assure the supervising engineer that the pile meets all design requirements including adequate geotechnical bearing capacity.
Similarly, devices are known which are used to monitor the pile after it is driven. This includes the Piscsalko patents which include devices that can be used to monitor the pile even after the driving process. Further, Mcvay, et al., U.S. Pat. No. 6,533,502 also discloses a device used to monitor a pile during or after the driving process is completed. The information produced by the systems can be used to determine the current state of the pile, including the geotechnical bearing capacity, and for determining a defect and/or damage, such as structural damage, that may or may not have incurred in response to any one of a number of events including natural disasters.
In addition, it is known in the art that devices can be used to help determine the structural integrity of a poured pile wherein the pouring of the pile and the quality of this pouring can determine the structural integrity of the pile once a poured material, like concrete, has cured. Mullins, et al., U.S. Pat. No. 6,783,273 attempts to measure this integrity of a poured pile by disclosing a system and method for testing the integrity of concrete shafts by moving a single thermal sensor arrangement up and down in a logging tube during the curing cycle of the concrete in the poured pile. Piscsalko U.S. Pat. No. 8,382,369 discloses an alternative to the Mullins device and discloses a thermal pile sensing device that includes one or more sensor strings, each with multiple thermal sensors, that are capable of monitoring the entire pile generally simultaneously and over a period of time and can create two or three dimensional images, in real time, based on the curing of the poured material to assess structural integrity and/or other structural characteristics.
However, while the prior art disclosed above can effectively measure the integrity of the pile and certain aspects of the borehole during or after the pouring of the pile, the bearing capacity of the pile is also and more usually dependent on the condition of the soil around the length of the shaft and below the bottom borehole before the pile is poured. The bearing capacity at the bottom of the borehole relates to the condition of the soil at the bottom of the borehole wherein loose soil has less bearing capacity than soils that are undisturbed or dense. Loose soil also contributes to undesirable increased settlement of the supported structure. Thus, it is best to reduce the amount of loose soil at the bottom of the borehole. In view of the difficulties associated with viewing the bottom of a borehole that can be many meters below the ground surface, and frequently in an opaque slurry condition consisting of suspended clay particles mixed in water, or possibly a liquid polymer mixture, it is common practice to employ a so-called “clean-out bucket” to reduce the amount of unsuitable bearing material, such as loose soil, at the shaft bottom. This procedure requires replacing the drilling equipment with the clean-out bucket, which is then lowered into the borehole. The success of the bottom cleaning is, however, not assured and several passes or cycles of this effort may be needed. The uncertainty can lead to unnecessary effort and, therefore, cost. Throughout the remaining specification of this application, the terminology “debris layer” and/or “debris” will be used to generally define the unsuitable bearing material above the bearing layer. The unsuitable bearing material includes, but is not limited to, loose soil, loose material, soft material and/or general debris. The debris together forms the debris layer. The same is true with the condition of the borehole wall wherein the condition and shape of the borehole wall is also a factor in the bearing capacity of the poured pile.
Therefore, there is still a need for a system to inspect the surfaces of a borehole before a pile is poured that reduces the complexity and cost of the system without adversely increasing labor costs by requiring highly skilled operators at the jobsite for long periods of time and working near the borehole. Yet further, there is a need for a system that makes it less costly to inspect the borehole bottom and/or sides and reduces the need for, or time required by, the secondary excavating system to clean up the debris on the bottom of the borehole.